A. Bielski

Effect of dissociative recombination on spectral line profiles in neon glow discharge

In the present study we have shown that the dissociative recombination of Ne2+ ions which gives rise to non-thermalized Ne atoms may be regarded as the main process responsible for the distortion of the profiles of the 753.5 and 754.4 nm neon lines. The distorted profiles were analysed as a superposition of the Ballik profile for thermalized atoms and the modified Ballik profile for non-thermalized atoms and the Lorentzian and Gaussian widths as well as the relative density of non-thermalized and thermalized atoms have been determined. We have found for the dissociation energy of the neon molecular ion Ne2+ in the 2 Sigma u+ state the value D=(1.20+or-0.08) eV. We have also found for the 3d6 excited neon atoms of speed 1275 m s-1 the excitation transfer cross section Q3d6 with a value Q3d6=(39+or-15)*10-16 cm2.

On the role of Dicke narrowing in the formation of atomic line shapes in the optical domain

The purpose of this work is to verify the possibility of the observation of the Dicke narrowing of atomic spectral lines in the optical domain. As an example we have chosen experimental results obtained by means of a laser-induced fluorescence method for the 114Cd 326.1 nm line perturbed by xenon. Experimental results were carefully reanalysed using a line shape model which takes into account the speed dependence of collisional broadening and shifting, the velocity-changing collisions and the collision-time asymmetry. We have found no convincing evidence for the occurrence of Dicke narrowing of the 326.1 cadmium line perturbed by xenon. The Dicke narrowing (if it occurs at all) appears to be smaller than that resulting from the estimation based on the accessible data describing the diffusion of Cd in Xe. As a source of this behaviour the correlation between velocity-changing and dephasing collisions was indicated.

Low pressure broadening and shift of the cadmium intercombination line 326.1 nm (5 1S0-5 3P1) perturbed by He and Ne

The collisional broadening and shift of the 114Cd intercombination line lambda =326.1 nm (5 1S0-5 3P1) perturbed by He and Ne have been investigated using a pressure-scanned Fabry-Perot interferometer. The values of pressure broadening and shift coefficients determined from the experiment compared with those calculated by Czuchaj and Sienkiewicz (1987) and with values resulting from the Lennard-Jones potential.

Response of scanning Fabry-Pèrot interferometer to the speed dependent Voigt profile

Abstract A detailed discussion of the influence of correlation effects on the combined Doppler and pressure broadening of spectral lines observed by means of a Fabry-Perot interferometer is presented. An expression for the response of scanning Fabry-Perot interferometer to the speed dependent Voigt profile is derived.

Low-pressure broadening and shift of 3p54s-3p5np (n=4, 5, 6) argon spectral lines perturbed by He, Ne, Ar

Low-pressure broadening and shift of three spectral lines of argon: 667.7 nm (3p54s-3p54p), 430.0 nm (3p54s-3p55p) and 360.6 nm (3p54s-3p56p), emitted from a low current glow discharge in pure argon, Ar-Ne and Ar-He mixtures have been investigated by means of a Fabry-Perot interferometer. The values of the pressure broadening and shift coefficients are determined.

Response of scanning Fabry-Perot interferometers to asymmetric spectral line profiles

A detailed discussion of the effect of adding the dispersion-shaped component to the Lorentzian profile on the resulting line profile recorded by an ideal scanning Fabry-Perot interferometer is presented. An analytic correction to the Ballik formula for the response of a Fabry-Perot interferometer is derived which makes it possible to determine quantitatively the magnitude of the collision-time asymmetry in the line profiles.

Method of accurately measuring the spectral line tilt in the Ebert spectrograph

A simple method for accurate spectral-line-tilt measurement in Ebert spectrographs is presented; it utilizes a special diaphragm situated in front of the entrance or behind the exit slit. This diaphragm splits the image of each tilted line into two fringes. The mutual distance is proportional to the exit slit tilt away from its position for which the line tilt is compensated.

Spectral line tilt effect in the Ebert spectrograph

In the Ebert spectrograph the spectral lines tilt away from the normal on the photographic plate when the grating is rotated. We have calculated this effect and compared it with the experimental data.

Isotope Structure and Hyperfine Splitting of 326.1 nm 113Cd line

In the course of this work the influence of the isotope structure of the 326.1 nm (51S0‐53P1) cadmium line on the resulting line shape was carefully studied. Measurements for the 113Cd line perturbed by Ne at low pressure (below 2 Torr) were used for determination of isotope shifts of cadmium hyperfine components. The results has been used as a starting point for the analysis of more than 90 spectra of the line under investigation perturbed by different gasses in wide pressure range. That allowed us to determine the hyperfine splitting for 113Cd 326.1 nm line with uncertainty below 10−3 cm−1.

Asymmetric line broadening

Using a laser-induced fluorescence method a detailed analysis of the profiles of the 114Cd326.1 nm line perturbed by all rare gases was performed which revealed departures from the ordinary Voigt profile. These departures are shown to be consistent with fits of experimental profiles to a speed-dependent asymmetric Voigt profile or asymmetric Voigt profile.